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ftrace/x86_32: Set ftrace_stub to weak to prevent gcc from using short jumps to it
With new binutils, gcc may get smart with its optimization and change a jmp from a 5 byte jump to a 2 byte one even though it was jumping to a global function. But that global function existed within a 2 byte radius, and gcc was able to optimize it. Unfortunately, that jump was also being modified when function graph tracing begins. Since ftrace expected that jump to be 5 bytes, but it was only two, it overwrote code after the jump, causing a crash. This was fixed for x86_64 with commit8329e818f1
, with the same subject as this commit, but nothing was done for x86_32. Cc: stable@vger.kernel.org Fixes:d61f82d066
("ftrace: use dynamic patching for updating mcount calls") Reported-by: Colin Ian King <colin.king@canonical.com> Tested-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -889,8 +889,8 @@ ftrace_graph_call:
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jmp ftrace_stub
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#endif
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.globl ftrace_stub
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ftrace_stub:
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/* This is weak to keep gas from relaxing the jumps */
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WEAK(ftrace_stub)
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ret
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END(ftrace_caller)
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